Project Summary Research into the proteins that cause neurodegenerative diseases is undergoing a remarkable transformation with the detailed identification of biochemical and biophysical pathways that drive neuron stress and death. Our work focuses on the cellular prion protein (PrPC), a ubiquitous protein of the central nervous system and peripheral tissues. Misfolding of PrPC to its scrapie form, PrPSc, causes a range of diseases including Creutzfeldt-Jakob disease (CJD), Fatal Familial Insomnia and Kuru. In addition, PrPC was recently identified as a primary receptor for A? peptide oligomers that drive cytotoxicity in Alzheimer?s disease. Our focus is two-fold: First, we wish to understand the function of this wide-spread protein, and second, we want to understand how aberrant signaling in prion diseases and Alzheimer?s disease leads to neurodegeneration. It is now well established that PrPC is a Cu2+/Zn2+-binding protein that controls the anatomical distribution of these essential metal ions in the brain. Through our long- standing grant GM065790-16, we have determined the coordination features of the metal ion binding sites, evaluated the detailed binding thermodynamics, and developed new concepts for understanding inherited prion diseases. Within the last few years, using magnetic resonance and electrophysiology, we uncovered an inter-domain interaction in PrPC, driven by metal ion binding, which regulates neurotoxicity. We are now positioned to pursue the molecular details of this interaction, as well as the role of varying metal ion concentrations, global protein fold, relevant post-translational modifications and disease associated mutations. In addition, it is now recognized that PrPC modulates the function of several transmembrane glutamate receptors ? we wish to identify the PrPC functional domains relevant to these important interactions. Our evolving paradigm of PrPC toxicity provides a platform for understanding neurodegenerative processes in both prion and Alzheimer?s diseases. Our request for MIRA funding is to enable the resources and flexibility so that we may work efficiently in this highly important and rapidly changing field.